My favorites...
DLR:
-Dole Whip Float (Tiki Bar, Adventureland)
-Mickey Beignet and Mint Julep (Mint Julep Bar, NOS)
-Raspberry Macaron (Jolly Holiday, Main Street)
DCA:
-Mac 'n Cheese Cone (Cozy Cone, Carsland)
-Starbucks Drinks (Three Pigs Cafe, Buena Vista Street)
DTD:
-Peanut Butter Heaven (Marceline's)
-Chocolate-Covered Caramel Apple (Marceline's)
Not park specific, but also yummy...
-Popcorn
-Churros